1. Field of the Invention
The present invention is directed to a power regulation feedback system and method for optimizing the robustness of data transmissions across a wireless communication link irrespective of the separation distance between antennas of respective active emitter and receiver devices relative to one another.
2. Description of Related Art
In a variety of scientific, industrial, and medically related applications, it may be desirable to transfer information and data via a wireless communication link. Use of wireless communication is receiving particular wide spread development in medical applications. Drug infusion pumps, pacemakers, sensors, stimulators, defibrillators and cochlear implants are just a few, but not an exhaustive list, of medically implanted systems in the human body employing wireless communication. Typically, such medical application systems include an external control device having a primary winding, coil, or antenna in wireless communication with an implantable medical device having a secondary winding, coil, or antenna. Each electronic device may have its own power source. Alternatively, RF energy or power may be transferred from an external power source to power the implantable medical device. A portable external device is preferred in most medical application systems and thus, will not remain at a fixed or permanent location relative to the internal device. For example, an implantable drug infusion pump may be programmed or controlled by a portable external device positioned to rest proximate or in direct contact with the patient's body. Due to the portability of the external device, the distance separation between the primary and secondary coils will vary relative to one another.
Variation in separation distance of the coils has heretofore been recognized to impact the power supplied by the secondary winding to a load (e.g., an implanted device) source whereby the implantable device may potentially function erratically or intermittently as a result of the inconsistent or unstable source of available power. Specifically, U.S. Pat. No. 6,442,434 discloses a method and apparatus for providing a sufficiently stable power to a load in an implanted device in a transcutaneous energy transfer system (e.g., a TET system). A power supply and a primary winding are located on a first side external to a body while a secondary winding is disposed on a second side internal to the body. Power from a power source external to the body is transferred to the internal device which does not have its own power source. The power supplied by the secondary winding to a load (e.g., an implanted device) may be quite sensitive to more than nominal or trivial physical displacements of either the primary winding or the secondary winding from an optimum coupling position. In view of the fact that the primary and secondary windings of conventional TET devices are not necessarily fixed in position with respect to one another, the power supplied by the secondary winding to a load (e.g., an implanted device) may not be consistent and stable. Unstable power sources can result in undesirable intermittent or erratic power being supplied to the implantable medical device possibly interrupting operation with potentially life threatening consequences. This issue determines the suitability of the TET technology to a particular type of load, e.g., those implanted device requiring a consistent source of available power. Accordingly, it is an object of this patented TET system to provide a sufficiently stable power from the secondary winding to the load. Specifically, the system regulates the primary amplitude such that the load voltage across the load approaches and approximates a threshold voltage in the secondary circuit. The distance separation between the antennas or coils may have deleterious effects on the system other than providing an unstable power to the load which are neither recognized nor addressed by the patented system.
Regulating the TET system to provide a sufficiently stable passive power supply produced by the secondary winding to the load, as in the patented system, is of little, if any, concern when the implantable device is designed with its own internal power supply. Nevertheless, in a wireless communication system changes in the relative position (separation distance) of the windings, coils, or antennas relative to one another has other detrimental effects that have heretofore not been addressed. As the distance between the antennas increases and thus the amount of energy induced in the secondary coil decreases wireless communication between the devices becomes less robust thereby increasing transmission errors and loss.
It is therefore desirable to develop an improved energy transfer system in which irrespective of the separation distance between the primary and secondary antennas or coils, robust wireless communication of digital data transmissions is optimized.